Persons with a hearing loss due to aging (presbycusis) or to noise exposure frequently complain of difficulty in understanding speech in a noisy environment. Previous investigations by Elliot and others have indicated that persons with sensorineural hearing loss have abnormalities in the temporal processing of acoustic signals in addition to their inability to detect sounds at normal intensity levels. The purpose of this project is to examine the target population's perception of auditory signals when temporal and frequency parameters are systematically varied. In the temporal integration studies, ability to detect a tone in the presence of continuous broad-band noise is measured as a function of the duration and frequency of the tone. The forward, backward, and gap masking studies measure detection of a brief tonal signal presented at various time intervals relative to the onset or termination of a long duration broad-band noise masker. All subjects are tested under all conditions with a standard two-alternative forced-choice procedure. Subjects are pledged to participate for three test sessions per week over a minimum period of six months. In the future, narrow-band maskers, as opposed to the broad-band masker of the above mentioned studies, will be used to simulate a more speech-like masking situation. With these investigations, the focus of the project will broaden to include abnormalities in the processing of frequency information in the context of temporal processing demands.